CVE-2026-70188

ASP.NET Core Security Feature Bypass Vulnerability

At a glance

Severity: CRITICAL 9.1
EPSS: EPSS 0.94 % · percentile 61 (2026-10-27)
State: PUBLISHED
Published: 2026-10-13
Updated: 2026-10-27
Assigner: microsoft
NVD status: Awaiting Analysis

Description

Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.

Scores

Version	Score	Vector	Scored by
CVSS 3.1	CRITICAL 9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C	microsoft
CVSS 3.1	CRITICAL 9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N	NVD · secure@microsoft.com (Secondary)

Weaknesses (CWE)

CWE-444

Advisories

GHSA-fpq8-4vhr-rcxx — Microsoft Security Advisory CVE-2026-70188 - ASP.NET Core Security Feature Bypass Vulnerability

European references

ENISA EUVD · EUVD-2026-99700
GCVE · GCVE-0-2026-70188

CERT-FR advisories

CERTFR-2026-AVI-1316 — Multiples vulnérabilités dans les produits Microsoft · cert.ssi.gouv.fr
CERTFR-2026-AVI-1313 — Multiples vulnérabilités dans Microsoft .Net · cert.ssi.gouv.fr

Affected products

Product	Versions
Microsoft · ASP.NET Core 10.0	affected 10.0 < 10.0.13
Microsoft · ASP.NET Core 11.0	affected 11.0 < 11.0.0-rc.2
Microsoft · ASP.NET Core 8.0	affected 8.0 < 8.0.32
Microsoft · ASP.NET Core 9.0	affected 9.0 < 9.0.21
Microsoft · Microsoft Visual Studio 2022 version 17.14	affected 17.14.0 < 17.14.42
Microsoft · Microsoft Visual Studio 2026 version 18.10	affected 18.10.0 < 18.10.4

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70188

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)	Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD